A clean room known heretofore is a room with air containing dust in low concentration (with a cleanliness class of about 10,000). Hence, dust contained in the air outside the clean room is removed by a dust filter, and the resulting air is supplied to the clean room. Recently, however, gaseous chemical substances such as ammonia, sulfur oxide, and organic solvents are increasing in the environment, and the concentration of such gaseous chemical substances is required to be reduced to several parts per billion (ppb) for the cleaned air supplied to the clean room.
In order to remove the gaseous chemical substances mentioned above, cation exchange fibers have been used to adsorb alkaline substances such as ammonia, or anion exchange fibers have been used to adsorb acidic substances such as sulfur oxides, and ammonia and sulfur oxides have been removed by using these ion exchange fibers in combination. Furthermore, ammonia and sulfur oxides have been removed together with an organic solvent by using active carbon carrying thereon an acidic substance or an alkaline substance.
However, ion exchange fibers as well as active carbon filters carrying thereon an acidic substance or alkaline substance, are not easily regenerated, and, in case the adsorbed gaseous chemical substances amount to a predetermined quantity or greater, in general, these fibers and filters must be exchanged about once a year. Furthermore, for instance, the two types of ion exchange fibers and active carbon filters must be prepared depending on the type of gaseous chemical substances, and the ion exchange fibers and active carbon filters are extremely expensive. As a measure to elongate the life of ion exchange fibers and active carbon filters, a method for removing, to some extent, ammonia and sulfur oxide easily soluble to water is proposed by setting a scrubber for spraying water to the stage prior to the removal of gaseous chemical substances. Still, however, the life of ion exchange fibers and active carbon have been found to be extended merely to about 2 to 2.5 times.
An object of the invention is to provide a clean room equipped with a cleaned air feeding apparatus in which adsorption and regeneration are carried out simultaneously, so as to enable semi-permanent use of the apparatus, and which is yet capable of removing all of the gaseous chemical substances.